


Foglight

by Mystic_Harley



Category: Doctor Who, Doctor Who & Related Fandoms, Harry Potter - J. K. Rowling
Genre: Crossover, One Shot, Sirius Being A Good Godfather, Suspense, mild body horror
Language: English
Status: Completed
Published: 2019-12-14
Updated: 2019-12-14
Packaged: 2021-02-25 04:55:33
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 7,748
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21790417
Author URL: https://archiveofourown.org/users/Mystic_Harley/pseuds/Mystic_Harley
Summary: An unnatural fog surrounds Hogwarts School for Witchcraft and Wizardry. The castle is eerily quiet, and Harry is left alone with only his godfather for protection. Something is tracking him, hiding in the fog.The only person Harry can think of to save them has arrived, but The Doctor isn't the one that Harry remembers, and it soon becomes clear that not even The Doctor can handle what has arrived.
Comments: 2
Kudos: 9





	Foglight

**Author's Note:**

> This is a sequel to my previous Harry Potter/Doctor Who crossover, Shadows of the Night, but you don't have to read that to read this!

Harry never understood the difference between fog and mist. It all looked the same to him as he stepped out in the cold noon Saturday morning, hugging his cloak and his scarf close to his body to keep himself warm. Hermione could likely tell him, he mused as he eyed the Dementors guarding the doors warily. Their featureless faces moved towards him and he was glad when the doors to the Entrance Hall groaned open and he felt the warmth of Fang whimpering at his heels a few moments later. The shadow of Hagrid a comforting presence. “Ar ye ready to go Harry?” His giant friend asked.   
  
He nodded, smiling at his giant friend despite the cold coloring his cheeks and nose. Saturday tea at Hagrid’s was a welcome relief from the fact that a mass murderer was gunning for his head, a fact that technically he wasn’t even supposed to know, for some unfathomable reason. Add to the fact that Uncle Vernon hadn’t signed his Hogsmeade Permission Slip (And he doubted, in hindsight, if it would’ve been accepted anyways) he found himself terribly alone at the castle.    
  
That was when Hagrid had invited him for afternoon tea. Harry honestly couldn’t think of much else to do other than fly around the quidditch pitch or browse the library so the idea of spending an afternoon with Hagrid was an appealing one, at the very least he could get entertaining stories about various magical beasts from him.   
  
“Did the Dementors cause this big fog?” He asked curiously, squinting into the bleak greyness of their surroundings, having to jog a bit to keep up with his friend’s huge gate. He remembered the swirling mist that accompanied them on the train and shuddered a bit.   
  
“Not anythin this thick. Rather odd that, we normally don’t get fog like this so soon.” Harry raised an eyebrow at him, but didn’t comment. Hagrid didn’t seem particularly worried, and that was enough for him. Hogwarts  _ was _ a magic castle after all, why should the weather not have a little something in it?    
  
Under normal circumstances, Harry would usually keep his questions to himself. The Dursleys had done a very good job at stamping out his natural curiosity, and yet that curious soul inside of him had begun to grow again recently. There were two reasons for this:   
  
One was that ever since his encounter with the Doctor and a brief glimpse of wonders even with magic he could never have dreamed of, he had started asking those questions that burned at the tip of his tongue that he always kept hidden. Even if the answer was never a completely satisfying one, he felt better knowing.   
  
Two was the big black dog that pounced on him the moment he opened Hagrid’s hut. He laughed out as the dog licked his face, ruffling his fur. “Snuffles! Snuffles down boy! I’m happy to see you too!”    
  
His real name was Sirius Black, the mass murderer that was supposedly after Harry’s head that very moment. There was a brief heart-stopping moment when the ratty and underfed dog suddenly turned into the most wanted wizard alive, and it had taken a lot of begging for Harry to agree to listen to him.    
  
Harry didn’t regret the choice to listen to Sirius, even if he  _ had _ made him swear to him by threat of losing his magic that what he was saying was the absolute truth. Harry really had no idea if that sort of oath was even feasible but regardless after hearing the truth and seeing the evidence, he knew Sirius’ answer hadn’t changed.   
  
Once he had gotten used to the fact he had a god-father, they quickly began making plans to obtain one Peter Pettigrew and clearing his name. This, unfortunately, was a lot easier said than done. While the actual act of smuggling Sirus  _ to _ Hogwarts was almost laughable; Hagrid was more than willing to take care of another dog for Harry, and he got to see him at least once or twice a week, the fact remained that they had no idea how to get the rat.    
  
Somehow, they had enlisted the help of Hermione’s cat Crookshanks in the operation but even with the feline providing crucial support, Peter wasn’t stupid and they were no further to this goal.    
  
But, none of that mattered to Harry. He had a  _ god father _ and he was a permanent, if surprising, fixture in his life. Getting letters and hearing stories about his parents’ time at Hogwarts was worth the tension knowing he was sleeping in the same room as his  _ true _ parents’ killer.   
  
“Awfully foggy day today, isn’t it Snuffles?” He muttered into the fur, rubbing his back and glancing out at the swirling void. He could barely make out what was right in front of his face. Even the castle herself was blocked out completely. At least, Harry noted, Sirius was recovering nicely. His fur didn’t look as ratty and there was some color in his cheeks when he was in human form.

  
The dog whined, and nudged Harry with his cold wet nose, which caused the boy to frown. “What, is something the matter?” The dog nodded, but before he could try and work out anything more Hagrid had bustled them inside and started the fire.   
  
“Awfully chilly now, I suspect it will be until ol Black is caught. Never did like those ruddy dementors. Spooks the animals.” Hagrid shook his shaggy head before putting a gigantic kettle on the crackling fire. Harry hiding his amused look by busying himself giving belly rubs to the dogs.    
  
“Do Dementors even affect animals?” Harry asked, and it had been a good question that they seemingly hadn’t zero’d in on Sirius anyways in dog form.   
  
Hagrid shrugged, sitting down in his chair and the wood groaned dangerous under his weight. “Prolly not, not much of a soul for them to steal. Yer better off asking Professor Lupin about tha’ though fer more details. Now, how ‘as school been for ye Harry?”   
  
Hagrid’s tea, unlike his rock cakes, was delicious. Harry felt himself warm up drinking the liquid has he informed Hagrid about how his classes were going, able to weedle out a few stories from his giant friend about a few of the upper-year classes.    
  
As tea was winding down, Harry jumped as both Snuffles and Fang bolted up and began barking loudly at the door. He shared a bewildered look as Hagrid got up and pulled the two away from the door. “Alright, alright you two! Settle down! Must be a dementor wanderin’ nearbye, I told you they spook the animals.” Harry had set his tea-cup down and went over to the window, peering out into the dense fog. If there were dementors there, he certainly couldn’t see them.    
  
Then, the fog moved. It swirled around and he saw a dark shadow move through it. His heart caught in his throat, watching in horror as  _ something _ seemed to manifest in the greyness A black, shadowy figure that he could barely describe properly before it vanished after a few seconds. He swallowed thickly, before glancing back at Hagrid. “Hagrid? I think I need to head back to the castle. You know how dementors tend to affect me more than others.”    
  
Hagrid jumped up and bustled Harry out of the cabin, Snuffles right on their heels as they tore through the fog. Harry kept his senses alert, trying to listen for any unnatural sounds as they crunched up towards the castle. Hagrid was mumbling under his breath and his heavy footsteps seemed painfully loud.   
  
They all froze when there was an unearthly, guttural rattle of  _ something _ off in the distance. Harry felt his blood turn to ice and he clung onto Hagrid’s arm tightly as there was another gurgling, inhuman rasp before it was quickly extinguished. “Hagrid…” Harry breathed. “What on earth was that.”   
  
“Harry, come on.” Hagrid had literally picked Harry up and began to run towards the castle. Snuffles hot on his heels and barking madly as the fog around them seemed even thicker than normal as the castle suddenly burst into view and Hagrid wrenched the giant doors to the entrance hall open like they were made of tissue paper. Snuffles skittered in as Hagrid put Harry down and slammed the door hard, the loud bang of the oak reverberating around the hall. There was the sound of a lock sliding into place, Hagrid’s keys jangling as they were hastily shoved back into his pocket.   
  
The fog had crept in from the cracks in the door and was permeating in the castle. Thick clouds rolled around and were billowing upwards to the rest of the castle. Harry felt a chill down his spine as looked around the normally lively castle. He could only hear the sound of Hagrid’s heavy breathing.   
  
Harry boggled up at his giant friend as Hagrid wheezed a little. He bent down and gave Harry a serious look, his beetle black eyes wide and it struck Harry that Hagrid was  _ afraid. _ “Harry, go straight up to your common room.”   
  
“But what abou-”   
  
“Don’t argue, Harry. Just do it!” Hagrid hissed. “Professor McGonagall will understand why yer dog is there, just  _ go! _ ” He straightened and began to march off, his vast form almost swallowed by the greyness.    
  
“Where are you going?” Harry called out, kneeling down and hugging his dog.   
  
“To get the headmaster, go to your common room!” Hagrid called back. Harry watched on helplessly as his giant friend disappeared into the fog, and left him and Snuffles standing there alone.   
  
“ _ Sirius. _ ” Harry hissed out, and instantly two thin arms wrapped around his own thin frame. Sirius Black hugged his godson close, stroking his hair. “Sirius what’s going on?”   
  
“I don’t know Harry.” He rasped out quietly. His scraggly hair hid his gaunt face as he looked around the empty entrance hall. “I really don’t know. I’ve never seen fog like this before. It’s certainly nothing the dementors could have caused.”   
  
“What was that sound we heard outside?” Harry glanced out at the door, his heart thumping loudly in his ears.    
  
“I don’t know.” Sirius admitted, hugging his godson close to him. “If only I had my wand… and don’t think for a second I’m taking yours.” He warned the boy. “Come on, we need to get you back to the common room. Come on, the fog is thick enough that I don’t need to hide just yet.” the two cautiously moved towards the staircase. The fog was so thick at the bottom that they had no idea how far it reached, and slowly they began their ascent.   
  
“If only the Doctor was here…” Harry muttered under his breath, knowing that if anyone would be able to figure out what was going on, it was her.   
  
“I sincerely doubt that she’ll be able to find her way here.” Sirius replied back darkly. “Hogwarts is warded to the gills. I can’t imagine how difficult it would’ve been for me to get in here without your help.”   
  
“You would’ve found a way, you’re clever like that. You escaped Azkaban didn’t you?” Harry replied back, hoping the fear in his voice wasn’t too obvious as they reached the first floor. “I can barely see anything, let alone where the staircase is…” He muttered, trying to peer into the grey to see where they had to go next.   
  
“Someone can get lost in Hogwarts even in full daylight.” Sirius agreed, frowning heavily. “But in this….” He sucked in his teeth a little, before glancing down at Harry. “Get your wand out. Maybe a little light will help us see.”   
  
Harry did as instructed, pulling his wand out and muttering  _ Lumos _ under his breath. He shied away from the light as it pierced through the gray haze, but much to his dismay, it didn’t do much to improve their situation. “ _ Lumos Maxima. _ ” A searing light exploded out of the tip of his wand, and he moved it outwards, squinting his eyes as it rolled through the fog, the light bright enough that it was able to cut through the haze slightly and illuminate the next staircase.   
  
Sirius clapped him on the back, and smiled proudly down at him. “Well done, Harry. Let’s get going. Make sure to keep the light close.”   
  
With his cheeks warm from the praise, Harry nodded and together they scaled up another flight of stairs and paused halfway when the loud shuddering  _ boom _ of the front doors being slammed echoed in the silence. They shared a look with one another and waited quietly. “ _ Nox. _ ” Harry whispered quietly. The light died out and the sound thundered out again, ancient oak groaning under enormous strain. Harry swallowed and looked up at his god-father as the moaning, gurgling noise of  _ whatever _ it was. “Sirius…”    
  
“Move!” Sirius hissed, and they hurried as quickly as they could dare up the stairs and peered out over the railing once they reached the second floor. “I hope Remus is in…” Sirius muttered, glancing down the grey corridor.   
  
“Will he be able to help us?” Harry asked, still staring down at the endless wall of fog that had invaded the castle.   
  
“Remus was always the expert when it came to the dark arts.” Sirius nodded, frowning heavily and leaning over a bit. “Can you hear that?”   
  
Harry paused and listened. At first he couldn’t hear anything but then he frowned as he heard the sound of… scraping. Of flesh scraping against stone. He swallowed and clung to his god-father tighter. “What the hell is that?” He breathed.   
  
“I don’t want to stick around and find out. Come on, lets-” He was cut off by the sound that made Harry’s heart soar with hope. The grinding, warbling sounds of what was unmistakably the TARDIS, off in the distance of the corridor. “Impossible..” Sirius breathed.   
  
“Come on! Let’s go get her!” Harry exclaimed, grabbing his hand and dragging Sirius into the DADA corridor. “Doctor? Doctor can you hear me? It’s Harry!” He called out, all sense of caution abandoned.    
  
“Harry keep your voice down!” Sirius hissed, running after him. “We don’t know what’s out there and we certainly don’t want whatever it is barging up here after the Doctor!” He sighed as Harry flushed with embarrassment. “Let’s just find her and ask for her help, shall we?”   
  
They walked in silence down the corridor and Harry realized to his horror that he had no idea where the TARDIS could have landed. He wasn’t even sure they were on the right floor, with how sound tended to bounce off of the walls. The only thing that kept his hope alive was that he was  _ sure _ the Doctor was here though.    
  
Then he heard the sound of voices. Pressing themselves against the wall, Harry strained his hearing to try and make out who was talking, their voices drifting out from the haze. “Do you have any idea where we are? It’s just as bad out here as it was in the TARDIS.” A young woman’s voice by the sound of it, nothing like the Doctor or Yaz’s though.   
  
Then, an older man’s voice. It sounded distinguished and refined. “No, I haven’t the foggiest.” There was a groan and chuckling from the voices as they got closer. “I’m serious, though. Even the scanners weren’t much use. It’s almost as if something was… was blocking our exact location. The TARDIS certainly didn’t like landing here.”   
  
Harry and Sirius looked at each other, and nodded. Harry stepped out, calling out in a quieter manner. “Hello? Is there anyone out there?” Sirius looked at him and Harry flushed, what was he supposed to say?   
  
“Oh, Hello? Yes we can hear you! Can you see anything?” The woman’s voice called out.   
  
“Not a thing!” Sirius replied back. “We’ll come to you.”   
  
“No need!” The man’s voice called out. “We’ll come to you, you sound relatively close. Come on, Jo, they shouldn’t be far. Do you have a light or something we can identify you with?”   
  
“Yes, one second!  _ Lumos! _ ”    
  
The harsh wandlight filled the corridor, casting shadows across Harry and Sirius’s faces. The woman’s voice gasped out, and the sound of heels clacking against stone grew louder. “Doctor, that was a spell! Oh we must be at Hogwarts!  _ Lumos! _ ”   
  
Two shadows finally formed in the darkness as another light exploded out a few meters away, and then they burst through the fog. The young woman had her wand out and high in the air. She was a dirty blonde woman, with a smile that lit up her face and clothes that walked straight out of Aunt Petunia’s old fashion magazines he saw her read.   
  
A tall, white haired man walked behind her. He had an old, wizened face that reminded him of a lot of Headmaster Dumbledore, with his intelligent eyes and grandfatherly smile. He wore dark red and black, a cape hanging around his shoulders. There was a look of recognition in his eyes as he approached and held out his hand. “Hello, this is Jo Grant, and I’m the Doctor.”    
  
Harry stared up at the man, mouth open in bewilderment as he took his hand. He shook it, but gave a confused look back at Sirius, who had his eyes narrowed suspiciously. “But.. but you’re not the Doctor.” He finally blurted out.   
  
The man’s face creased, his brow furrowed in confusion. “Oh? And why can’t I be, hm? Last time I checked I was.”   
  
“It’s just…” Harry floundered, looking back at Sirius again to make sure he wasn’t crazy. “The Doctor was a woman, last time I met her. Isn’t that right Sirius?”   
  
The man’s eyebrows rose a little in surprise, then he rubbed his chin thoughtfully. “A woman, eh? Last time I checked I was never a woman, so that means.” He sighed a little, then rubbed his neck. “Well, that’s something I’m looking forward too.”   
  
Jo frowned, glancing at her older companion curiously. “What does that mean, Doctor? I met both of your younger selves and none of them was a woman, does that mean…”   
  
“Yes, Jo. It appears that young Mister Potter here has met a future version of myself, and apparently that version is a woman.” He smiled kindly at Harry, and then peered curiously at Sirius. “You must be Sirius Black then.”   
  
Harry could feel Sirius tense under the supposed Doctor’s scrutinous gaze, and he moved instinctively in front of his godfather to protect him. “He’s innocent.” He said darkly.   
  
“Oh yes, I’m perfectly aware of that. And I don’t think you’re the cause of this fog either, far too much energy for even a wizard such as yourself to be capable of doing. Isn’t that right Jo?”   
  
Jo shrugged, and glanced at Harry and Sirius. “Are these two… you know.. Important?” There seemed to be some different meaning behind her words, her eyes flickered to Harry’s scar. Normally he hated this sort of attention but he was surprised when instead of an understanding or wide-eyed look, she only got even more curious. “You obviously know them Doctor, but I’ve never heard of either of them.”   
  
“No, I suspect you haven’t Jo. We’re a few decades past your own time. 1993, if I have my dates right.”    
  
Harry blinked in shock, and looked at Jo curiously. “You’re not from this time period?”   
  
Jo laughed, and shook her head. “I’m afraid not, I went to Hogwarts in the 60s, and it’s the 70s where I’m currently from. Or was from.” She frowned suddenly, before shaking her head. “Well, it doesn’t matter anyways. Has the old castle changed much? If it wasn’t for this blasted fog I could be able to tell.”   
  
“It hasn’t changed all that much.” Sirius confirmed, still eyeing the Doctor warily. “I probably came into school just as you were graduating, you don’t look that much older than I do.”   
  
Jo laughed a little. “I suppose you’re right, it just seems like such a long time ago.”   
  
They all froze when they heard the gurgling noise again. The scraping, disgusting sound of flesh on stone. “Damn!” Sirius hissed,pushing Harry behind him. “I had forgotten all about it!”   
  
“All about what?” Jo asked, wand pointed outwards towards the corridor. “What on earth was that sound?”   
  
“That’s just it, we don’t know!” Harry piped up, a little annoyed that the adults were shoving him away from the action. “We were hoping you did, or we could find Professor Lupin.”   
  
The Doctor carefully inched out so he was standing next to Jo. Trying to peer into the fog, he squinted and angled his head before jumping slightly as the gurgling sound grew louder. “Jo, is there any way you can clear this fog?” He asked.   
  
“I can try, let’s see here…” She flicked and waved her wand in completely silence. Harry watched in astonishment as the fog suddenly  _ whooshed _ to either sides of the corridor, piling up as if someone had packed it all against the wall tightly. “That can’t hold for long-oh my goodness!”   
  
It was a dementor. Or at least, something that  _ looked _ like a dementor to Harry. It’s cloaked was ripped and tattered, a black substance oozing out of its mouth and it  _ rasped _ as it clawed its way towards them. Fog seemed to be pouring out of its orifices, and it reached a long, clawed hand out towards them before slapping it against the stone.    
  
The Doctor stepped forward, staring intensely at the creature. Jo began to move closer and the Doctor thrust his hand out. “Stay back!” He barked sharply, shuffling a bit closer.    
  
“Doctor, it looks like a dementor.” Jo’s voice was shaky, her wand trembling ever so slightly.    
  
“That’s no dementor I’ve ever seen, and believe me, I’ve seen quite my share in Azkaban.” Sirius replied, staring in horror at the disgusting thing. “It doesn’t feel like a dementor though. It’s… it’s almost like it’s…”   
  
“Mutated.” The Doctor noted, curiosity bleeding into his tone as he stared in fascination at the creature. “But dementors aren’t actual creatures, not in the literal sense at least. They  _ can’t _ mutate. So what are you…” He jumped back when a long clawed hand swiped out again, and the fog suddenly slammed back around them, even thicker than before. Harry couldn’t even see where the adults had gone. “Jo! The fog!” The Doctor called out.   
  
“I couldn’t maintain it!” Jo called back. “Whatever this thing is, it just… stopped it!”   
  
“Everyone back away slowly. Follow the sound of my voice.” The Doctor’s sounded out, and the sound of footsteps alerted Harry that he was moving behind them. “Come on everyone, just follow me. What floor are we on, Mister Black?”   
  
“Second. I think Remus’s office is somewhere along there. Perhaps if we can find it…” Sirius’s voice trailed off, unsure.   
  
Now he was alone again. The fog was getting worse and Harry couldn’t hear the… the dementor  _ thing _ over the sound of his breathing anymore. His heart pounded in his ears and he pressed himself against the wall, inching along it and desperately trying to find a door he could hide behind.   
  
“Harry? Harry are you still there?”   
  
“Here…” He croaked weakly, and almost screamed when Jo’s figure burst through the heavy mist. Immediately, she wrapped her arms around him in a protective hug. “What in Merlin’s name was that creature?”   
  
Jo glanced around, holding up her wand and pressing herself against the wall, keeping a tight grip on Harry’s hand. “I don’t know, but right now I don’t care. We need to find The Doctor and Mr. Black, they said they were going to someone named Remus’s office?” She inclined her head, gently tugging Harry to follow her as she inched along the wall.   
  
“He’s our Defense Against the Dark Arts teacher.” Harry informed her, creeping along with her and trying to keep his hearing strained for any sound of the creature. “Like Sirius said, his office is on this floor. Although I don’t think I can tell which door is his in this fog..”   
  
“Then we’ll just have to try them all until we find the right one.” Jo said sternly. “Now hold on tight and follow me.” She held her wand out in her palm and whispered something to it, the wand spinning like a needle before settling on a direction. Gripping it tightly, she lead Harry into the grey shadows and before long a large oak door swam into view. She pushed at it and it swung open easily.   
  
They couldn’t see anything from the doorway other than the swirling fog all around them. Looking at each other, they nodded and ran into the room together, wands at the ready before screeching to a halt as Harry banged his legs on a desk and swore loudly.   
  
“Looks like an empty classroom.” Jo noted, walked around the desk and carefully feeling her way around. “Is this the DaDa room?”   
  
It was hard to tell in the fog, but after some squinting Harry shook his head, sitting on one of the desks and rubbing his bruised knees. “No, Professor Lupin’s classroom isn’t as bare. There are tanks and skeletons hanging around the room. He’s got a very special interest in dark creatures, our third year has mostly been studying them.”   
  
Flicking her wand to shut the door, Jo sat down on the desk next to Harry and laughed a little. “That sounds far more exciting than my third year here. I can barely remember what our third year teacher was like, they kept having to replace them every year.”   
  
“They still do that.” Harry confirmed, smiling a little at the knowledge that some things never really changed around Hogwarts. “Last year we had some dunce named Gilderoy Lockhart, and the year before that we had a nutcase who had Lord Voldemort in the back of his head.”   
  
Jo’s reaction to the name ‘Voldemort’ was surprising to Harry. Most people jumped and flinched at the mention of his name like it was a particularly bad swear word, but Jo simply tilted her head in confusion at the mention of it. “Voldemort…” She repeated slowly, glancing off to the side. “I can’t say I’ve heard of the name, but it does seem familiar…”   
  
“Well, I think he was just starting to rise to power when you were...er..are…” He petered off lamely, before coughing. “In the 70s. So it makes sense you haven’t heard of him.”   
  
“Oh no, I’m out of touch with the wizarding world these days.” Jo brushed him off, laughing a little. “I still keep up with my magic, of course but it’s been quite a long time since I could use it. UNIT is a science based organization after all, not a magical one.”    
  
Harry had never heard of UNIT before but he assumed that must be something in the government based on that kind of response. He nodded, feeling a chill run through him again. “Hey Jo? Do you mind if I ask you a question?” At her affirmative, he looked down at his feet, watching the fog swirled around them, as he kicked one up, the fog puffed into the air slightly before reforming back into the shapeless void. “What house were you sorted in?”   
  
“Hufflepuff. Proud of it too.” She leaned over, a curious sparkle in her eye. “You’ve met another version of The Doctor, right? What was she like?”   
  
He shrugged, kicking out at the fog again. “She was really nice. She helped me out of a sticky situation, it’s actually how I met Sirius.” He sighed a little, feeling a lump in his throat that refused to go away no matter how hard he swallowed. “And now this happens…Before I could even prove he was innocent…”   
  
He felt something warm in his hand, and he glanced over to see Jo holding it. “Harry, look at me.” He looked up, taken aback by the fire suddenly burning in her gaze. That fierce determination that he had seen on The Doctor’s face when he first met her. “You and Mr. Black are going to get out of this alright. I promise you.”   
  
Harry nodded, feeling a hope blossom in his chest. They shared a smile, and for a brief moment briefly forgot the situation they were both in until the door exploded out in a violent shower of splinters. Harry nearly fell off the desk as the dark shape of the  _ thing _ slapped wetly onto the stone floor and began crawling towards them. “Harry, get back!” Jo called out, brandishing her wand and jabbing it at the creature. “Expecto Patronum!”   
  
Unable to see the silvery-white patronus that had burst from Jo’s wand, he could only watch on in fascinated horror as it slammed into the creature and phased right through like it was nothing, and he squeezed down the urge to scream as he saw the creature rear up from the floor and emit a teeth-numbing rasp of breath and the silver-white energies sucked into its mouth, black liquid dripping from its empty eye-sockets onto the ground.    
  
Jo gaped at the creature, unable to comprehend what had just happened for a few precious moments. “It  _ ate _ my patronus!” She exclaimed indignantly, then snapped her wand down with an angry expression. One of the desks immediately flew forward and crashed against the creature as it was reaching out towards a petrified Harry, sending it skittering to the floor. “Run!” She yelled, grabbing his hand and tearing out of the room before the creature had time to recover. They sprinted down the hallway, uncaring about which direction they were going until they burst out of the hallway and onto the staircase landing again. “Come on, upstairs.” She began bustling him up the staircase, which swung around for them like it had previously.   
  
“But The Doctor and Sirius!” Harry protested, unwilling to leave his godfather alone with whatever that hell creature was.   
  
“Are more than capable of taking care of themselves. Sirius may not have his wand but he’s still an adult. And The Doctor would never let anything happen to him anyways. Right now we need to make sure you’re safe Harry.” Jo said firmly, dragging him up the staircase and onto the third floor, the staircase swinging back around to provide them some extra safety.   
  
“If only I had the map…” Harry grumbled, glancing over the railing again just to see that they weren’t being followed.   
  
“There’s a map of the school?” Jo asked in amazement, leading him through the third floor cautiously. “That certainly would have come in handy while I was still in school.”   
  
“Erm, it’s not an official map. My dad, Sirius, and Professor Lupin made it when they were at school. It would be nice to have it though, we could track where we are on the map.” He frowned, glancing up at her. “We’re on the third floor, right?”   
  
“I assume so, we only went up one flight of stairs.”   
  
Harry nodded slowly, closing his eyes and trying to remember what happened on his first year. “If I remember right…” He said slowly, opening his eyes and grabbing Jo’s hand. “I think I know how we can give that thing the slip.” Tugging on her arm, he lead her down the foggy corridor, mentally counting the doors as they swam into focus and then disappeared again into the grey. “There’s a secret passageway in the trophy room, it leads to the fourth floor.” He explained, stopping at the right door and swinging it open. “Come on, let’s find something to block the door in case it comes up here.”   
  
“What on earth are we going to block the door with? The trophies?” Jo asked in confusion, looking around the empty room.    
  
Harry pursed his lips unhappily, slowly reaching his hand out and pressing it against one of the display cases. The glass felt ice cold to the touch, and it stung his hand a little but he refused to let it go. “Why not one of the suits of armor in the armory? It’s connected to the trophy room, I think.”   
  
“Excellent idea Harry.” Jo complimented, flicking her wand and flinching as the loud screech of metal scraping against the floor echoed across the room as a suit of armor was dragged across the floor and collapsed in a heap against old wood of the door. “Well, hopefully that provides us a bit of leverage, I don’t think I can repeat that desk trick again here.”   
  
“We just need to find the secret passage way.” Harry reassured her, feeling along the outer edges of the glass cases, his reflection staring back at him in the glass. “It leads to the fourth floor, we can hide in the Hospital Wing there. Madam Pomfrey should still be there, I think.”   
  
“You mean to tell me she’s still working here?” Jo asked in surprise, hugging herself against the glass cases. “What exactly am I supposed to look for anyways? What does the entrance look like?”   
  
“A portrait, some guy named Brutus Scrimjour I think. I never paid that much attention to the name truthfully.” Harry said, still feeling along the edges of the cases until he hit the wall. He swallowed, trying to remember the password as he kept searching. If he couldn’t remember it, then their best hope was to double back and try the staircase.   
  
When there was a loud crash against the door, he soon scrapped that plan.   
  
“Come on… come on…” He urged himself quietly, frantically pacing against the wall and dragging his hand across a giant mirror that he knew connected to the armory. “Where are you…?”   
  
“Mr. Scrimjour!” Jo called out loudly from the other side of the room. “Mr. Scrimjour are you there?”   
  
To his eternal relief, there was the sound of spluttering from the other end of the hall, near the back of the armory. “My name, young lady, is Brutus  _ Scrimgeour _ and I would be very pleased if you wouldn’t butcher my family name!” Sprinting over to the sound of the portrait, he jumped when he heard the loud crash of wood as the door was rocked open, glass shattering as undoubtedly the suit of armor was thrown across the room. A noble looking man with a thin mustache and drooping wizard’s hat peered at them from his portrait. “I was Headmaster of this school once, you know. I won’t do with having my name garbled up.”   
  
Red faced, out of breath, and completely panic laced, Harry moved along the edges of the portrait, trying to pry the passage open as his brain refused to give him the password needed to open it. “Come on, open! Open!”   
  
“We’re terribly sorry Headmaster.” Jo soothed quickly, pulling Harry back before he ripped the painting off the wall entirely. “But I’m afraid our lives are in mortal danger, and the only way we can escape is through the passageway you guard. We don’t know the password, could you please open the way for us?”   
  
There was a brief, agonizing silence as the portrait stared at the two of them. The heavy sounds of flesh ripping and scraping against broken glass and stone pierced the air. “Please Headmaster!” Harry begged.   
  
Finally, the portrait swung open. “Inside you two, quickly!” The portrait called. “I’ll alert the current Headmaster of your whereabouts, I assume you’re going to the hospital wing. Move!”    
  
Saying their brief thank yous, they sprinted into the dark and mercifully fog-less corridor. The cracks were too thin for even the fog to penetrate and as the door swung shut behind them they were plunged into total darkness until Jo held up her wand and the tip lit up softly. She reached out with her other hand and grabbed Harry’s, guiding him through the dank smelling cavern and up a mossy set of stairs until they reached the top and pushed open another door.   
  
They peered out cautiously as the fog battered their faces again. Harry’s eyes and nose stung from the sudden chill that washed over him but for the moment it appeared they were safe until they heard the rattling of the creature behind them. “Why can’t it leave us alone?” Harry moaned, hauling out of the passageway and down the corridor towards the Hospital Wing, knowing full well the creature was closing in on them with an almost dogged determination.    
  
When they reached the doors, they found to their frustration they were locked. Harry shook the doors violently, pounding on them and yelling as loud as he could. “Madam Pomfrey! Let us in! We need help!” He pounded on them again, hoping that the matron would hurry up and open the doors as the rasping, gurgling noises grew louder.   
  
Jo pointed her wand at the door and flashes of light started illuminating the fog around them, but when she tried to open the doors they remained firmly shut. “That’s strange, the hospital wing is never locked!” She exclaimed.   
  
“Well clearly it is now!” Harry called back in frustration, the hysteria in his voice reaching a peak when he saw the creature’s form start moving through the fog. His throat closed up as it approached them, dripping that same disgusting ichor and despite not having any legs it managed to rise up anyways and loom over them. Harry swallowed thickly and squeezed his eyes tightly, hoping beyond hope that something would come and save him. He didn’t want to die.   
  
“GET AWAY FROM MY GODSON!”    
  
There was a loud, vicious bark as a black furry object slammed into the creature. Harry’s eyes flew open as Professor Lupin and The Doctor ran into view, followed closely by Headmaster Dumbledore. “Doctor!” Jo called, but Harry’s eyes were glued to the struggling mass of bony flesh and fur as Sirius in his dog form was thrown off and into the fog.   
  
“Sirius!” Harry cried out in alarm, moving to go after him until Jo forced him to stay put.   
  
“Jo! Get Harry back!” The Doctor called out, brandishing a device that Harry didn’t recognize. “Professor, Headmaster, on my count! One…” They both pulled their wands out and at the creature. “Two…” The Doctor’s thumb hovered over the button. “THREE!”   
  
There was a loud, high pitched scream from the device. Harry clapped his hands over his ears and was afraid his glasses would break from such a high frequency as Professor Lupin and the headmaster both yelled a spell he couldn’t understand and a great flash of silver light engulfed the entire corridor. The creature howled in agony, writhing around on the floor as black ichor spurted out of it like a geyser. The Doctor yelled something Harry couldn’t hear and there was a brilliant flash of gold.   
  
The creature stopped moving, and then was still. The Doctor shut off his device and Harry lowered his arms. “Is.. is it dead?”   
  
“Yes Harry, it is.” The Doctor confirmed, stepping over the body of the creature and placing a hand on Jo’s shoulder. “Are you alright, Jo?”   
  
“Just a little shaken up, but otherwise fine.” She answered, pulling him in for a fierce hug anyways. As The Doctor hugged her back, she stared down at it. “What on earth was that thing Doctor?”   
  
The Headmaster cleared his throat at that moment. “I believe Miss Grant, explanations can be withheld for just a touch longer while we get young Mr. Black, Mr. Potter, and yourself in the hospital wing. I believe some hot cocoa would do all of us a world of good right now. And might I say, you look rather exceptional for your age Miss Grant. Why, I would even go so far as to say you haven’t aged a single day since I last saw you.” His eyes twinkled fiercely as he tapped the doors to the hospital wing and they glided open.    
  
Harry clung onto Sirius for dear life as he helped him limp into the hospital wing. The fog seemed to be lessening up now that the creature was dead. With a simple wave of his wand, the headmaster opened the windows and the fog began funneling out. Harry helped Sirius lay down in one of the beds and held onto him tightly. “Are you okay?”   
  
Sirius snorted, ruffling his godson’s hair affectionately. “It will take more than some strange and unknown creature to keep me down. What I’m more concerned about is your safety, Harry. Are  _ you _ okay?”   
  
“I am now that you’re here.” He said, laying his head on his godfather’s chest.    
  
With a little smile on his face, Professor Dumbledore clapped his hands and waved them. An immaculate tea tray appeared before them, and with a simple command of “Hogwarts’ finest hot chocolate please!” it was packed with steaming mugs of cocoa. After passing the drinks around, the Headmaster sat down on a chair he conjured for himself. “I believe, Doctor, you would be best to explain the creature and how it came to be. It was you who figured out what had happened.”   
  
The Doctor stepped forward, rubbing his neck slightly and clearing his throat. “Yes, well, it was rather simple in hindsight. You see, after we got seperated, Mr. Black and I had managed to find a dead dementor, of all things, laying in the hallway. Now what would, or could kill a dementor?” He seemed to be enjoying himself, pacing slightly.   
  
Jo frowned, taking his question into consideration. “I thought dementors couldn’t die though. I think if they could be killed the Ministry would have tried a long time ago, right?”   
  
Nodding at his companion, The Doctor gave her a little smile. “Quite right Jo, but this time was different. The dementor seemed to have been… consumed, somehow. Obviously Hogwarts has nothing in either the lake or the forest that would be able or willing to come near a dementor but this year was different, for there was one thing that would do so: Another dementor.”   
  
His audience of two gawked at him for a moment, Harry’s mouth moving up and down but making no sound. Ultimately, it was Jo who finally spoke up again. “You.. you mean to tell me that that creature we saw, the one that had been chasing us, was a  _ cannibal dementor? _ ”   
  
“Precisely.” The Doctor beamed. “It was so desperate for food, so in need of souls that it resorted to trying to eat one of its own kind. The dementors usually stick around Azkaban for a reason, you know. Without the natural black magics surrounding the island that sustained them as well as the prisoners, a few of them weren’t able to cope with the lack of food and began starving. Now, ordinarily a hungry dementor would simply go on a feeding frenzy on humans, but in this rare circumstance, it fed on its own kind.”   
  
“And the result was what we all witnessed out in the hall.” Professor Lupin added from his seat, sipping on his hot cocoa and not taking his eyes off of Sirius. “I was conducting my own investigation into what was going on with the Headmaster when I ran across Sirius and The Doctor here. From what we’ve been able to gather, when a dementor feeds on its own kind, it starts… what was the term you used?” He asked The Doctor   
  
“Imploding.”   
  
“Yes, imploding on itself. The black ichor was about the closest thing to blood that the dementor had, and while normally cold and able to produce a slightly foggy effect already, that was enhanced by the fact it had consumed another of its kind. Resulting in the thick blanket that has covered the castle.”   
  
Harry blinked owlishly, looking between his teacher, his headmaster, and The Doctor from where he sat, sipping on his chocolate. “But, how did you stop it then?”   
  
“We had discovered that high sonic frequencies disrupted the creature.” The Doctor explained, pulling out his device. “With my sonic screwdriver, I was able to heavily disorient it. It was Mr. Black that made the connection that a concentrated blast of patronus energy combined with the sonic blast would be enough to kill it.”   
  
“The gold spell was really just to make sure it would stay dead.” Lupin commented. “A powerful but effective spell designed to restart patient’s hearts at hospitals. Naturally, that type of spell is normally not taught to the general populace but Headmaster Dumbledore was kind enough to share the secret in this time of duress.”   
  
Harry’s eyes darted back and forth between everyone again, gripping his mug tightly. “So… is that it then? Are we out of danger?”   
  
The Doctor smiled at Harry and it was then that Harry truly realized that The Doctor he met just a few months ago and one standing before him were the same person. The same warmth in his smile, kindness in his eyes and the burning intelligence. “Yes, Harry, I believe we are out of danger. I think it’s time we should be leaving, Jo.”    
  
Jo pulled Harry in for a quick hug, and smiled at him. “It was wonderful meeting you Harry, you keep on your studies for me alright? And keep Sirius out of trouble.”   
  
Harry smiled and watched as the two travelers said their goodbyes and left the hospital wing. The doors swung shut but even so Harry could hear the faint grinding engines of the TARDIS, taking Jo and The Doctor off to who knows where or when.   
  
“Now then,” Dumbledore began jovially, sipping his own cocoa and looking at Harry over his half-moon spectacles. “I believe Mr. Potter, you owe us an explanation for how you discovered not only Mr. Black was your godfather, but to inform us on why you believe he happens to be innocent.” He raised his hand as Harry began to protest. “Now my boy, I’m not going to lock Mr. Black up just yet, despite my misgivings. He was the one to risk himself by begging for our help after all, and he did just save your life. So I am willing to hear you out.”   
  
Harry closed his mouth, and stewed for a moment. He glanced at Sirius, who nodded at him encouragingly. Taking a sip of his cocoa, he set the cup down and leaned forward. “How I first met Sirius is a bit odd, sir. You see, when I was at Little Whinging ...”

**Author's Note:**

> Thank you for everyone who read this, this took longer than I would've like but I'm very proud of the end result. Reviews and comments are always appreciated.


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